FORTÉ LIVING – AUSTRALIA’S FIRST MULTIRESIDENTIAL CLT BUILDING

Some five years after its completion, and as the use of mass timber building systems increases, Forest and Wood Products Australia (FWPA) looks back at the design and build of Australia’s first CLT apartments.

Forté Living is a 10 storey, 23 apartment building constructed from Austrian-sourced cross laminated timber (CLT). Standing at 32.2m it was the world’s tallest modern timber apartment building and the highest made from CLT. It was also the first Australian building to be made from CLT.

THE MATERIALThe building comprises 759 CLT panels of European spruce (picea abies), weighing a total of 485 tonnes. The spruce was grown and harvested in Austria. The panels were manufactured then shipped to Australia in 25 shipping containers.

The building arrived like flat pack furniture, including the 5,500 angle brackets and 34,550 screws required for erection.

THE BUILD
Forte’s ground floor and first storey floor slab were constructed from geopolymer concrete. This was due to the larger spans required in the retail space and general good design practice to isolate timber from the ground.

Once the concrete had set, the CLT panels were transported from their storage site, a disused wharf shed a short distance away. One of the challenges faced by the construction team was sequencing the panels so that they would be delivered to the site in the order required for erection.

Once on site, the panels were raised into their final position by an electric crane fuelled by biodiesel, then connected with screws and metal brackets.

The first panels erected were those that formed the stair and lift cores and these were positioned vertically. Once the cores were in place, subsequent panels were placed horizontally to form internal and external walls. The panel width is the storey height of the building.

Panels were then laid on top of the walls to form floors. The process was step-repeated until the full height of the building was reached. The roof was constructed in the same way as each of the floors.

Finally, the exterior cladding was applied as the scaffolding and screen were removed, revealing the building as it was ‘unwrapped’.

THE EXTERIOR
The exterior of the building is clad with metal commercial façade consisting primarily of AluBond. Some parts were also covered with Lysaght and recycled hardwood timber.

These finishes provide the rain screen to the CLT structure.

The balconies are extensions of the CLT flooring of the main structure. The CLT is covered with screed and a water proof membrane, then finished with tiles.

The underside of the CLT used in the balcony floor is exposed. With a timber stain and polyurethane seal protecting the timber, no additional protection was required.

Forte building interior

ENVIRONMENTAL ADVANTAGES
Forté positively affects the environment by directly storing (sequestering) 761 tonnes of CO2. When considering the emitted CO2 that would occur if an equivalent concrete or steel buildings was used, the advantage increases to 1,451 tonnes of CO2 or the equivalent of taking 345 cars off the road for a year.

Using timber for a building the size of Forté is estimated to save 7.7 ML of water and lower eutrophication (the supply of excess nutrients to the water system) by 75%.

In addition, the smart design and efficient systems of the building are estimated to save residents an average over $300 per year on energy and water bills.

Forté targeted a 5 Star As Built Green Star building in Australia.

DURABILITY
CLT is made from European spruce which is considered as non-durable i.e. Class 4 timber. Protection from termites and weather were the two key durability issues addressed.

Termite protection is provided by a concrete slab at ground level and then protected by TermiMesh. This is similar to the way in which a normal residential building is protected.

Protection from weather is achieved by a rain screen of aluminium panels. Supplementing this is a cavity between the rain screen panels and CLT that allows any water to drain out.

ACOUSTICS
The system used in Forté meets and exceeds building code deemed to satisfy minimum requirements. The floor uses a combination of products to deal with airborne sound as well as impact noise. The floors in the living area are engineered timber and, like any hard surface floors, require greater impact noise consideration. This project used techniques such as concrete screed topping, direct fixed and or resilient mounted plasterboard and suspended ceiling and resilient mat to improve airborne and impact noise.

FIRE RESISTANCE
As the building has a Rise in Storey of 9, it is Type A of Construction. Type A construction deemed-to-satisfy (DtS) provisions limits the use of timber in some applications.

Type A construction DtS provision places limits on the materials that can be used in the building construction as well as the level of fire resistance required.

The use of CLT cannot comply with the non-combustible DtS provisions of the National Construction Code (NCC). To meet the NCC an Alternative Solution was proposed to satisfy the relevant performance provisions.

In addition, the design solution ensured that:
Structurally, the building has been designed through disproportionate collapse. That is, the CLT structure has been analysed to ensure that should a wall section be damaged, the remaining structure is able to take the load.

Fire resistance is initially achieved through the direct fixing of fire grade plasterboard combined with the charring of the timber, ensuring that the structural component required is maintained through the provision of sacrificial layers.

The connections of the wall panels to floor panels maintain the appropriate fire ratings through by being incorporated within the centre layer of the panel or through being covered by screed / fire grade plasterboard.

The fire isolated stair shaft and lift shaft used a double shaft system in which each shaft achieves the required fire rating, however each does not rely on the other for structural connection. ■